Back and forth the Amerind race moved, up and down, across the face of the American continent through the forgotten ages in ever shifting waves impelled, in the main, by climatic conditions and food quest, some leaving behind no record, others bequeathing to the future monuments and edifices that astonished the world and gave birth to elaborate and far-fetched theories to account for a development that seems to have required no more than time and the circumstances which existed. All the remains on this continent appear to be palpably American; the work of the Amerinds in their various degrees of progress. Whether they came from one source or several, they have been long enough here to become homogeneous from one end of the hemisphere to the other, and this, it is evident, would require a great stretch of time.[9] They clearly separated from the other inhabitants of the world, in any case, at a period before those inhabitants had developed present characteristics. From the time the human race was born, whether as an ape or as it now stands, there was differentiation of habits, customs, and knowledge which has never ceased and which never will cease. But as light, air, and natural conditions are similar or the same the world round, and as cerebral matter seems to be practically the same in all peoples, humanity has passed everywhere through about the same stages of development, and each stock or tribe in time has arrived at about the same place on the road of progress because they could not help it. Conditions might force one people ahead while other conditions might be retarding another, but whatever progression there has ever been was made on practically the same lines. The same race, however, does not throughout always develop evenly. Sir John Lubbock has said that “different races in similar stages of development often present more features of resemblance to one another than the same race does to itself in different stages of its history,” and to-day in Arizona there exist near to each other two branches of the widespread Shoshonean[10] stock, the Pai Utes and the Mokis, who exhibit the most marked differences of customs, the latter living in substantial houses of stone while the former occupy the rudest kind of brush wikiups. [Illustration: A KIESKABI, OR COVERED PASSAGE, AT WALPI, ARIZONA]